The invention relates to a nozzle system for a delivery device for liquids, wherein the nozzle system comprises a nozzle and a device which fixes the nozzle in the delivery device. The delivery device, an atomizer, has a liquid reservoir from which a liquid is forced through the nozzle under pressure. The nozzle fixing means may itself be secured by a second fixing, e.g., in the form of a check nut, or the fixing may itself be a check nut. According to the invention the fixing means on the nozzle outlet side has a specific geometry which minimizes the amount of dispensed liquid deposited on the fixing means.
Preferably, the present invention is part of a propellant-free device for nebulizing pharmaceutical fluids. A nebulizer according to the invention is used, for example, to produce an aerosol of droplets for inhalation through the mouth and pharyngeal cavity into the lungs of a patient, for nasal administration or for spraying the surface of the eye.
WO 91/14468 discloses an apparatus for propellant-free administration of a metered quantity of a liquid pharmaceutical for application by inhalation. A further development of the device is described in detail in WO 97/12687. Reference is specifically made to these publications and the technology described therein is referred to within the scope of the present invention as Respimat™ technology. This term refers in particular to the technology which forms the basis for a device according to FIGS. 6a and 6b of WO 97/12687 and the associated description. Propellant-free liquids can easily be atomized using such devices.
In an inhaler of this kind liquid pharmaceutical formulations are stored in a reservoir. From there, they are conveyed through a riser tube into a pressure chamber from where they are forced through a nozzle.
The nozzle is held by a nozzle holder and the latter is secured by a check nut. The check nut has a liquid inlet side and a liquid outlet side. On the liquid inlet side is an opening through which a liquid from the pressure chamber can enter the nozzle. On the opposite side, the end face of the nozzle, the liquid then passes through two nozzle apertures which are aligned so that the jets of liquid leaving the apertures strike one another and are thereby atomized. The nozzle apertures are arranged in the inhaler in such a way that they are in direct contact with the outer environment.
This is achieved by the fact that the entire region of the nozzle holder and check nut which is located above the nozzle apertures has a recess (or hole or bore) through it which provides a pathway for a jet of liquid leaving the nozzle or an emerging aerosol to leave the atomizer through the mouthpiece.
In the region of this nozzle holder this recess is funnel-shaped while in the region of the check nut this recess is in the form of a uniform cylinder. The transition between the nozzle holder and check nut has a sharp edge so that the cross section of the recess is like an L in which the crossbar is inclined slightly downwards. The entire recess in front of the nozzle aperture, which is made up of the recess in the nozzle holder and the recess of the check nut, has a point of discontinuity in the elbow region of this L: the recess expands discontinuously, i.e., viewed from the base it first of all widens out and then bends sharply vertically in the region of the transition from the nozzle holder to the check nut. The vertical direction corresponds to the direction of spraying of the emerging liquid, i.e., the perpendicular to the outside of the nozzle (end face).
These inhalers normally deliver formulations based on water or mixtures of water and ethanol. They are able to nebulize a small amount of a liquid formulation in the therapeutically required dosage within a few seconds to produce an aerosol suitable for therapeutic inhalation. With the device, quantities of less than 100 microlitres can be nebulized, e.g., with one spray actuation, to produce an aerosol with an average particle size of less than 20 microns so that the inhalable part of the aerosol corresponds to the therapeutically effective amount. In these nebulizers with Respimat™ technology a pharmaceutical solution is converted by high pressure up to 500 bar into a low-speed aerosol mist destined for the lungs, which the patient can then breathe in.
A small amount of the liquid may be deposited from the outside as a film or as an accumulation of small droplets on the end face of the nozzle or on the end face of the fixing means for the nozzle or on the inside of the mouthpiece. This fraction of the liquid is also referred to as the mouthpiece fraction within the scope of this specification. This mouthpiece fraction reduces the amount of liquid dispensed, with the result that the inhalable fraction of the quantity delivered is reduced by the mouthpiece fraction.
The amount of liquid deposited need not be constant in every spray actuation but may depend on numerous factors such as the spatial orientation of the device during the aerosol production or the ambient temperature, relative humidity, etc. This leads on the one hand to a certain variability, however minor, in the amount dispensed which is then available for the patient to take in (delivered dose). Of the delivered dose, some has such a small particle size that the particles can be breathed deep into the lungs and this fraction is known as the inhalable fraction. However, the present specification does not expressly differentiate between the inhalable fraction and the total quantity of aerosol available for the patient to breathe in unless otherwise stated or unless clearly apparent from the context.
The liquid deposited may also cause contamination of the outer surface of the nozzle system or of the mouthpiece, which may in turn affect the pharmaceutical quality of the next aerosol mist.
Although these two effects are only slight in devices using Respimat™ technology it is important for reasons of quality control to minimize such effects.
It has now been found that in devices of this kind for dispensing liquids the proportion of liquid deposited on the outside of the nozzle system can be reduced by the particular geometry of the nozzle or nozzle fixing means. In fact, it has been found, surprisingly, that the mouthpiece fraction can be reduced if the entire area above the nozzle aperture (i.e., the area through which the dispensed liquid “flies” on its way to the mouthpiece) is funnel-shaped and has no edges.